Ma Chaoqiong, Yang Xiaofeng, Setianegara Jufri, Wang Yinan, Gao Yuan, Yu David, Patel Pretesh, Zhou Jun
Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, GA 30322, United States of America.
Department of Radiation Oncology, University of Kansas Medical Center, Kansas City, KS 66160, United States of America.
Phys Med Biol. 2024 Dec 3;69(24). doi: 10.1088/1361-6560/ad95d6.
We previously developed a FLASH planning framework for streamlined pin-ridge-filter (pin-RF) design, demonstrating its feasibility for single-energy proton FLASH planning. In this study, we refined the pin-RF design for easy assembly using reusable modules, focusing on its application in liver stereotactic ablative body radiotherapy (SABR).This framework generates an intermediate intensity-modulated proton therapy (IMPT) plan and translates it into step widths and thicknesses of pin-RFs for a single-energy FLASH plan. Parameters like energy spacing, monitor unit limit, and spot quantity were adjusted during IMPT planning, resulting in pin-RFs assembled using predefined modules with widths from 1 to 6 mm, each with a water-equivalent-thickness of 5 mm. This approach was validated on three liver SABR cases. FLASH doses, quantified using the FLASH effectiveness model at 1-5 Gy thresholds, were compared to conventional IMPT (IMPT-CONV) doses to assess clinical benefits.The highest demand for 6 mm width modules, moderate for 2-4 mm, and minimal for 1- and 5-mm modules were shown across all cases. At lower dose thresholds, the two-beam case reduced indicators including liverand skinby >19.4%, while the three-beam cases showed reductions⩽11.4%, indicating the need for higher fractional beam doses for an enhanced FLASH effect. Positive clinical benefits were seen only in the two-beam case at the 5 Gy threshold. At the 1 Gy threshold, the two-beam FLASH plan outperformed the IMPT-CONV plan, reducing dose indicators for all relevant normal tissues by up to 31.2%. In contrast, the three-beam cases showed negative clinical benefits, with skinand liverincreasing by up to 17.4% due to lower fractional beam doses and closer beam arrangements.This study evaluated the feasibility of modularizing streamlined pin-RFs in single-energy proton FLASH planning for liver SABR, offering guidance on optimal module composition and strategies to enhance FLASH planning.
我们之前开发了一种用于简化针状脊形滤波器（pin-RF）设计的FLASH计划框架，证明了其在单能质子FLASH计划中的可行性。在本研究中，我们改进了pin-RF设计，以便使用可重复使用的模块进行轻松组装，重点关注其在肝脏立体定向消融体部放射治疗（SABR）中的应用。该框架生成一个中间强度调制质子治疗（IMPT）计划，并将其转换为单能FLASH计划的pin-RF的步长和厚度。在IMPT计划期间调整了能量间距、监测单位限制和光斑数量等参数，从而使用宽度为1至6毫米、每个水等效厚度为5毫米的预定义模块组装pin-RF。该方法在三个肝脏SABR病例上得到了验证。使用FLASH有效性模型在1-5 Gy阈值下量化的FLASH剂量与传统IMPT（IMPT-CONV）剂量进行比较，以评估临床益处。在所有病例中，对6毫米宽度模块的需求最高，对2-4毫米模块的需求适中，对1毫米和5毫米模块的需求最小。在较低剂量阈值下，双束病例的指标包括肝脏和皮肤减少>19.4%，而三束病例的减少⩽11.4%，这表明需要更高的分次束剂量以增强FLASH效果。仅在5 Gy阈值的双束病例中观察到了积极的临床益处。在1 Gy阈值下，双束FLASH计划优于IMPT-CONV计划，所有相关正常组织的剂量指标最多降低31.2%。相比之下，三束病例显示出负面的临床益处，由于较低的分次束剂量和更紧密的束排列，皮肤和肝脏最多增加17.4%。本研究评估了在肝脏SABR的单能质子FLASH计划中模块化简化pin-RF的可行性，为优化模块组成和增强FLASH计划的策略提供了指导。
